New study finds magnetic fields affect oscillation frequencies in neutron star mergers.
Magnetic fields may alter neutron star vibrations after a collision.
Photo Credit: ESA
Magnetic fields may significantly complicate how scientists interpret gravitational wave signals from neutron star mergers, a new study has revealed. These collisions, where two super-dense stellar remnants merge, have long offered astrophysicists a way to probe matter under extreme pressure. The results from the University of Illinois Urbana-Champaign and the University of Valencia reveal that robust magnetic fields form more complex and lengthy patterns in gravitational waves, thereby making it harder to decipher the inner workings of neutron stars. Results could doom post-merger signal interpretation strategies and the equation of states of dense matter as scientists prepare to observe the next generation of gravitational wave observatories.
As per the study published in Physical Review Letters, the researchers simulated general relativistic magnetohydrodynamics — how the strength and arrangement of magnetic fields affect the frequency signals from the remnants left behind after a merger. They went represent real-world conditions by applying two different equations of state (EoS) for neutron stars, different magnetic field configurations, and several mass combinations.
According to lead researcher Antonios Tsokaros, the magnetic field can cause frequency shifts that can misidentify scientists into misattributing them as indications of other physical phenomena like phase transitions or quark-hadron crossover.
The discoveries also imply that scientists need to be cautious about how they interpret signals from neutron-star mergers, lest they slip into assuming how they form. They found that strong magnetic fields can change the emitted signals' typical oscillation frequency, shifting them from what they should be and from what was predicted by one or another of the competing equations of state at play within these ferocious events.
They also discovered that in the most straightforward type of galaxy mergers they considered in their simulations, the magnetic field became overly amplified so that a greater proportion of the remnants of the merger are more likely to produce further gravitational wave emissions.
Neutron stars are what remains of massive stars that have collapsed, and they contain matter so dense that a full teaspoon would weigh billions of tonnes. They have thermodynamic properties that are determined by the EoS and magnetic fields, some orders of magnitude stronger than those that one can produce in a human laboratory.
These extreme features also make neutron stars useful for probing the laws of physics under intense pressure and magnetism. Ever since it was detected in both gravitational waves and gamma rays in 2017, the scientific community has been buzzing about research on neutron star mergers, leading to ever-growing numbers of studies related to these types of mergers.
Professor Milton Ruiz also warns that it would be a mistake to misinterpret observations in the future without considering the effects of the magnetic fields. Higher-resolution simulations are needed, the researchers said, to refine our understanding of how magnetic fields shape cosmic happenings, and endeavours like the Einstein Telescope and Cosmic Explorer loom on the horizon.
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